1. Field of the Invention
The present invention relates to a manufacturing method for a magnetic head supporting suspension built in an information processing apparatus, such as a personal computer, and a suspension assembly including a load beam blank and flexure blank.
2. Description of the Related Art
FIG. 4 shows a part of a hard disk drive (HDD) 1. A carriage 2 of the disk drive 1 is turned around a shaft 2a by a positioning motor 3, such as a voice coil motor. The motor 3 comprises magnets 4. The carriage 2 comprises a coil portion 5 located near the magnets 4, arms 6, suspensions 7, magnetic heads 8, etc. Arms (or actuators) 6 are fixed to the coil portion 5. The suspensions 7 are mounted on the arms 6, individually. The magnetic heads 8 are located individually on the respective distal end portions of the suspensions 7. If the carriage 2 is actuated by the motor 3, each magnetic head 8 moves to a desired track (recording surface) of a disk 9.
Each magnetic head 8 comprises a slider 10 and a transducer (not shown) disposed on the slider 10. The slider 10 is disposed in a position where it can face the desired track of the disk 9. If the disk 9 rotates at high speed, an air bearing is formed between the slider 10 and a surface of the disk 9, and the slider 10 flies slightly above the disk surface. The height of this flight is called a flying height.
FIG. 5 shows an example of a prior art suspension 7′. FIG. 6 shows a gimbal portion of the suspension 7′. The suspension 7′ comprises a load beam 11, flexure 12 fixed to the load beam 11, and baseplate 13. The load beam 11 is a precise thin-plate spring. The flexure 12 is a plate spring thinner than the load beam 11. The baseplate 13 is fixed to the proximal portion of the load beam 11. The load beam 11 comprises a beam body portion 11a to which the flexure 12 is fixed, proximal portion 11b to which the baseplate 13 is fixed, and hinge portion 11c. The hinge portion 11c connects the body portion 11a and proximal portion 11b and serves as a spring. In another example of the suspension, the body portion 11a, proximal portion 11b, and hinge portion 11c are formed independently of one another. In this case, the body portion 11a, proximal portion 11b and hinge portion 11c are referred to as a load beam, base member, and hinge member, respectively.
The slider 10 is mounted on a tongue portion 12a that is formed on the distal end portion of the flexure 12. The stiffness of the flexure 12 is considerably reduced to allow the slider 10 to change its posture while it is flying above the disk 9. The load beam 11 and flexure 12 are superposed as they are fixed to each other by laser welding or the like. The flexure 12 shown in FIG. 6 is a so-called “flexure with conductors”, which comprises a conductive member 12b. 
A dimple 14 is disposed on the distal end portion of the load beam 11. The dimple 14 is a hemispherical protuberance projecting toward the slider 10. Since it is hollow on the backside of the load beam 11, however, this protuberance is referred to as a “dimple” in the art. The tip of the dimple 14 contacts the tongue portion 12a of the flexure 12. Thus, the magnetic head 8 can be displaced three-dimensionally in a pitching direction (indicated by arrow P in FIG. 6), rolling direction (indicated by arrow R), etc., around the dimple 14. The dimple 14 may be provided on the tongue portion 12a of the flexure 12 instead of being disposed on the load beam 11.
In fixing the load beam 11 and flexure 12 together, they need to be accurately positioned with respect to each other. Conventionally, for this purpose, reference holes 15 and 16 (FIG. 7) are bored through the load beam 11 and flexure 12, respectively. A jig pin 17 can be inserted into the reference holes 15 and 16. The load beam 11 and flexure 12 are clamped between a pad 18 and retaining member 19. In this clamped state, the load beam 11 and flexure 12 are fixed to each other by laser welding or the like.
In the prior art example described above, the load beam 11 or flexure 12 may be damaged by the jig pin 17 as the pin is inserted into reference holes 15 and 16. To avoid this, clearances should be secured between the outer peripheral surface of the jig pin 17 and the respective inner peripheral surfaces of the reference holes 15 and 16. In this case, as shown in FIG. 8, the reference holes 15 and 16 may be laterally dislocated by a margin corresponding to clearances C1 and C2. Thus, the load beam 11 and flexure 12 are decentered for (C1+C2)/2 at the maximum.
If the dislocation (or decentering) occurs between the load beam 11 and flexure 12, moments on the slider 10 are unbalanced. It is known that the flying height properties of the slider 10 relative to the disk 9 are greatly influenced by the moments on the slider 10. Thus, in order to obtain stable flying height properties, the moment in the rolling direction, in particular, should be prevented from becoming unbalanced.
The unbalance of the moment in the rolling direction is attributable to the static roll angle and dislocation of the dimple. In an example shown in FIG. 9, a dimple 14 is disposed on a flexure 12. In this case, the eccentricity of the flexure 12 relative to the load beam 11 directly causes a dimple dislocation ΔD, and the moment is unbalanced. In an example shown in FIG. 10, a dimple 14 is disposed on a load beam 11. In this case, the eccentricity between the load beam 11 and flexure 12 causes a moment deviation ΔM. Thus, unbalance of the moment attributable to the static roll angle occurs.
In order to obtain stable flying height properties, therefore, the eccentricity between the load beam 11 and flexure 12 needs to be minimized. Thus, it is very important to align the constituent members of the suspension with one another. In particular, high alignment accuracy is required for the relative positions of the dimple and the tongue portion of the flexure on which the slider is mounted. Actually, however, the accuracy of assembly of the load beam 11 and flexure 12 varies, so that it is difficult to obtain stable flying height properties.
If the relative positions of the load beam 11 and flexure 12 are misaligned, the following problems occur. With the recent demand for smaller heads, flexures with conductors have been put to practical use. In the suspension comprising the conductive member 12b, as shown in FIG. 6, for example, electrode pads 12c are mounted on the flexure 12. Thus, dislocation of the flexure 12 relative to the load beam 11 causes dislocation of the electrode pads 12c. In some cases, this dislocation may hinder the connection between the electrode pads 12c and terminals 8a on the head 8.
Jpn. Pat. Appln. KOKAI Publication No. 2000-163904 (Patent Document 1) discloses a suspension of which a load beam and flexure can be positioned with respect to each other. In this suspension, as shown in FIG. 11, a pair of reference holes 20 and 21 are formed in one of a load beam 11 and flexure 12. A pair of burred holes 22 and 23 comprising projecting edges 22a and 23a are formed in the other of the load beam 11 and flexure 12. The load beam 11 and flexure 12 are positioned by inserting the projecting edges 22a and 23a of the burred holes 22 and 23 into the reference holes 20 and 21, respectively.
If the burred holes 22 and 23 are formed in the load beam 11 or flexure 12, however, contamination may be caused around them during their burring work. Further, contamination may also be caused when the projecting edges 22a and 23a are inserted into the reference holes 20 and 21, respectively. The contamination is harmful to disk drives. With additional miniaturization of modern suspensions, moreover, the pitch between the reference holes 20 and 21 has been reduced so much that it has become difficult to obtain satisfactory positioning accuracy.
Jpn. Pat. Appln. KOKAI Publication No. 2002-133808 (Patent Document 2) discloses a suspension in which the pitch between reference holes can be widened. In this suspension, as shown in FIG. 12A, reference holes 15a and 15b are formed in a load beam 11 and one of junctions 11d, respectively. Likewise, reference holes 16a and 16b are formed in a flexure 12 and extending portion 12f, respectively. A hinge portion 11c is formed independently of the load beam 11. As shown in FIG. 12B, the load beam 11 and flexure 12 are superposed on each other, and a first jig pin is then inserted into the reference holes 15a and 16a, and a second jig pin into the reference holes 15b and 16b. In this state, the load beam 11 and flexure 12 are laser-welded together. Thereafter, the junctions 11d are cut off, whereupon the suspension shown in FIG. 12C is completed. However, even this example is not a solution to the problem of the clearances between the reference holes and jig pins.
In the suspension of which the load beam 11 and hinge portion 11c are formed independently of each other, moreover, the flexure 12 is expected to be accurately positioned with respect to the load beam 11 and hinge portion 11c. 